A sheave having a diameter 40 times or more the diameter of a rope has been conventionally used in an elevator apparatus in order to prevent early abrasion or breakage of the rope. Therefore, in order to reduce the diameter of the sheave, it is also necessary to make the diameter of the rope smaller. However, if the diameter of the rope is made smaller without changing the number of ropes, then there is a risk that a car may more easily vibrate due to load variations caused by baggage loaded in the car or passengers getting on and off the car, and rope vibrations at the sheave may be transmitted to the car. Further, an increase in the number of ropes results in a complicated structure of the elevator apparatus. In addition, if the diameter of a driving sheave is made smaller, driving frictional force is reduced. As a result, the weight of the car needs to be increased.
As means for solving such problems, it has been proposed to use a rope obtained by: twisting a plurality of steel wires together to form strands; twisting a plurality of the strands together to forma wire rope; and covering the outermost periphery of the wire rope with a resin material (for example, see Patent Literature 1). An elevator using such rope is driven by a frictional force between a sheave and the resin material forming the outermost periphery. Therefore, it is desired to stabilize or improve the friction characteristics of the resin material. Accordingly, in order to improve the friction characteristics of an elevator rope, it has been proposed to use a rope covered with a polyurethane covering material containing no wax (for example, see Patent Literature 2).
In general, the friction coefficient of a resin material is known to heavily depend on sliding velocity and temperature. Further, viscoelastic characteristics such as dynamic viscoelasticity of the resin material are known to have velocity and temperature dependencies which can be converted into each other (Williams-Landel-Ferry equation (WLF equation)). In addition, such conversion is achieved for the sliding velocity and temperature as well in the case of rubber friction, and hence it has been shown that the viscoelastic characteristics of rubber are involved in the friction characteristics of the rubber (for example, see Non Patent Literature 1).    [Patent Literature 1] Japanese Patent Laid-Open No. 2001-262482    [Patent Literature 2] Japanese Patent Laid-Open No. 2004-538382    [Non Patent Literature 1] Grosch, K. A.: Proc. Roy. Soc., A274, 21 (1963)